Vapor intrusion is a process by which chemicals (e.g., volatile organic compounds (VOCs), methane, radon, etc. . . . ) in soil and/or groundwater mitigate to or seep into building spaces. These vapors can be released from contaminated soil and/or groundwater underneath buildings, and may enter basements, crawl spaces, rooms and/or other areas of a building or structure. As a result of vapor intrusion, the air within buildings may become contaminated thereby exposing individuals within the buildings to chemical contamination, such as VOC and/or radon contamination.
Generally, VOCs are man-made chemical compounds that have a high vapor pressure and low water solubility. VOCs can be used and produced in the manufacture of fuels, paints, pharmaceuticals, and refrigerants, and are typically included in industrial solvents, paint thinners, tetrachoroethene (dry cleaning fluid), fuel oxygenates (MTBE), and by-products produced by chlorination in water treatment. VOC contaminants can travel with or on top of groundwater, and can easily become gaseous and migrate through soil. As a result of negative pressures that are induced by various building designs and features, VOCs can be drawn from the soil and/or groundwater, and into occupied spaces of buildings where human exposure can occur.
Radon is a Class A carcinogen that, according to scientific studies, can cause harmful effects on human lung tissue. Like VOCs, radon can be drawn into buildings from the underlying soil and/or groundwater by the negative pressures that are associated with the structure and features of buildings. Negative pressure can be caused by factors such as: temperature differentials where warm air exits an upper portion of a building (induces a stack effect), and wind and exhaust appliances that create additional vacuum. These forces can draw in VOC and or radon gases through cracks, conduit openings and other pathways in slabs, sub-slabs or other flooring features of buildings.